Radio beacon with quadrant identification



Jan. 16, 1945. ALFORD 2,367,177

' BEACON WITH QUADRANT IDENTIFICATION Filed Dec. 17, 1941 FIG.1. 4

RADIO J0 l/ASE EAL A/VCfF MQDUA 1470/? Tame-(mom) SOURCE IN VEN TOR. fl/VD/PEW AL FORD ATTORNEY.

Patented Jan. 16, 1945 RADIO BEACON WITH QUADRAN T IDENTIFICATION Andrew Alford, .New Xork, .N. .Y., assignor .to Federal Telephone and Radio Corporation, a corporation of -Delaware Application December 17, 1941,;Serial.No.-423,252

.7 Claims. .(.Cl. 250-11) This invention relates to radio range beacons and more particularly to two-course radio range beacons provided with quadrant identification means.

Radio beacons providing-sharply directed twocourse guide lines have been proposed in the past. -One difficulty encountered whenusing these beacons particularly for radio range purposes is that an aircraft coming within the field of the beacon cannot be sure of his location with respect to the beacon location. In other words, he can "tell when he is on one side or the other of the range defined by the beacon but cannot ascertain which direction along the range corresponds to his position. This difficulty can be overcome if some means is provided for identifying the "quadrants so that the'pilot will know his position 'angles to that defined by the main beacon. This second radio beacon is'keyed or otherwise provided with identifying signals to distinguish it from the main beacon and is adjusted preferably to transmit only side band energy to prevent "unwanted interaction between the carrier frequen- 'cies on the main course.

According to a further feature of my invention I provide means for minimizing interaction between the two radio beacon arrangements to further prevent undesirable interference alon the course. I

While I have outlined above the general -fea- -tures and objects'of my invention'a better'understanding may be had from the particular description made with reference to the accompanying -drawingin which Fig. 1 is a schematic wiring diagram of a radio beacon made :in accordance with my invention, and

Fig. 2zis a diagram of the field patterns for the purpose of explaining the operation of my invention.

Turning to the drawing, reference character I designates a radio frequency, source from which ---en.ergy is :fed through modulators l and ll and aa balancing network I2 to the three antenna units 2, .3 and 4 of-the :main two-course radio beacon. This radio beacon is of the type generally similar to one previously proposed. It should bedistinctly understood, however, that this illustration is made merely as an example and other known types of radio beacons may be used. Radio frequency energy modulated :attwo frequencies Fl, F2, which may for example, be

"and cycle notes are .fed directly to central radiator 3 over line ll, with the carriers in phase and from this central radiator the carrier frequency .as well as :the modulation side bands are radiated. The energy fed .to radiators .2. and 4 contains no carrier frequency but substantially only the -modulation side bands provided by modulators l0 and H. The feed line between radiators 2 and 4 isprovided with a transposition .so that these units which as :shown are loops for radiation of horizontally polarized energy, are fed in phase opposition.

Loops 2 and dare preferably spaced'a distance in the order of .165 electrical degrees from central radiator 3. The central radiator 3 in this instance should preferably have no parasitic effeet on side radiators 2 and 4, since it must also supply carrier for the quadrant identification beacon to be later'describe'd. This elfect maybe accomplished by making line I2 which interconnects these two radiators electrically equal :to an integral multiple of half-wave lengths. By making the lineofsuchalength, the center-point at which feeding occurs is effectively a short circuit. Accordingly, the junction point of line l2 with each of the feed lines to antennae 2 and 4 then looks like an opencircuit so far as radiators 2 and 4 are concerned and no parasitic effect is produced in the side radiators. While this point may be ascertained by calculation, it has generallyzbeenfound that the precise connection point maybe more readily determined experimentally. .Antenna :2, for example, isdisconnected from all the feed lines .and :energy is supplied only to central radiator .3. A short circuiting bar is then placed across line H and its position adjusted until meter readings show no energy in loop 2. .A..similar procedure is then effected for radiator 4. The two ,pointsfound by the short circuiting bar are then joined and line H is-couplecl at this junction point.

The beaconarrangementof radiators 2, 3 and .4, then produces --substantially the pattern v20E! shown in solid lines in Fig. .2 neglecting minor .lobes. This .isthe-normal two-course beacon pattern and :has :the drawbacks outlined above.

Inuorder to produce the rquadrant identificationl provide-a :second beacon arrangement consistingof antenna uni-ts 2A, SAand 4A, arranged at right angles to beacons 2, 3 and 4, and preferably at a different level therefrom so that loops 3 and 3A, are vertically spaced one above the other. Energy from source i is fed to balanced modulator H5 in which it is modulated by tone energy from source 15, for example, at a thousand cycle note. The output from the modulator 14 therefore consists of side band energy only.

The side band energy from I4 is fed over line HA directly to central loop 3A and is fed through a keying switch I6 and line I2A to the two side radiators 2A and 4A. Switch I6 is preferably arranged to produce interlocking keying signals such as A and N. However, if desired, any different keying signals may be produced so long as proper identification may be produced thereby. The tie line I2A interconnecting radiators 2A and 4A, is preferably made to have the same charac- I teristic as tie line I2, that is so as to produce no parasitic action in radiators 2A and 4A.

The radiators 2A and 4A are preferably spaced closer to one another than are radiators 2 and 4. The reason for this closer spacing is that the field produced by the auxiliary identification beacon is at right angles to the normal course line. As a consequence the minor lobes are 'of greater importance and a narrow spacing is providedto reduce the amplitude of any such minor lobes. The spacing of antennae 2A and 4A from'central antenna 3 is preferably made between 90 and 120 electrical degrees.

With this second beacon arrangement'a pattern such as shown in dash lines at 20! of Fig. is produced. It can, therefore, be seen that-in quadrant NW the 90 cycle and A signal predomi-'- nate, in quadrant SW the 150 cycle and A signal predominate, in quadrant SE the 150 cycle and N signal predominate and in quadrant NE the 90 cycle and N signal predominate. As a consequence the pilot flying into the range of the beacon will be immediately apprised of his position with respect to the beacon itself and the 180 degree ambiguity is fully overcome.

While the beacon described above is useful without any furtherchanges it can be realized that some reaction between loops 3 and 3A will occur. As a consequence some of the energy from loop 3 may be fed directly to loop 3A and vice versa. This leads to some confusion due to overlapping of the signal patterns. may be overcome by feeding some of the energy supplied to loop 3 to loop 3A and vice versa-in an amount just sufficient to compensate for the interaction. To accomplish this a line I8 is coupled to an intermediate point of feed line I"! and to an intermediate point of feed line HA supplying energy to antennae 3 and 3A, respectively. Line I8 may be provided with a phase shifter [9 if desired and the position of the connection point of line l8 and line HA, as well as adjustment of the phase shifter is made until there is no effective reaction remaining between loops "'3 and 3A. With this adjustment then the effective broadening of the coursesby interaction is com- 2 are clearly defined. I v While I have described above aparticular embodiment of my invention in connection with the preferred inserted diagram, it should be -under stood that this description is made by way of illustration. It should also be distinctly understood that the provisions for-preventinginter action between antenna unitsof an array -may be useful in connection with other combinations pletely overcome and patterns-200 and 20! of Fig.

than that illustrated. Furthermore, the broad of radiators, a source of radio frequency energy, I

first modulation means for applying distinctive signals tosaid radio frequency energy, means for applying said distinctively modulated signals to said first plurality of radiators to produce distinctively modulated overlapping fields of radio frequency refining a course line, a second plurality of radiators arranged transversely of said first set of radiators, a tone frequency source, a. balanced modulator coupled to said radio frequency source and said tone frequency source to produce side band modulation energy, said keying means for applying said side band modulation energy to said second plurality of radiators in alternately different phase relation to produce effectively overlapping fields of energy transversely of said distinctively modulated The difficulty" fields.

2. A radio beacon comprising a first set of .three radiators arranged in a line, a radio frequency source, means for modulating energy from .saidradio frequency source with two distinctive modulation signals, means for supplying the modulated energy to said radiators in phase revvlation to produce two effective overlapping fields of energy defining a course line, a second set of.

three radiators arranged in a line at substantially right angles to said first named line, a source of tone frequency, means for modulating energy from said radio frequency source with said tone frequency to produce substantially only side band energy, means for-supplying said side band energy to the center radiator of said second' set, and means for applying said side band .energy in alternately phase reversed relation to radiated energy.

.4. A radiobeacon according to claim 2, further comprising'means for feeding energy between'the central antennaeof said first and second sets, and means for adjusting the phase and amplitude of said,fed energy to neutralize parasitic intercoupling of said radiators.

5. A radio beacon according to claim 2, further comprising means interconnecting theouter radiators-of said, first and second sets respec- ,meansrfor' feeding energy between'the central antennae of said-firstand second sets; and means foradjusting the phase and amplitude of said energy to neutralize :par'asitic intercouplingof said radiators.

6. .A radio beacon comprising a central radiator, a pair of side radiators spaced on opposite sides of said central radiator, means for supplying energy to said central radiator, and to said side radiators, and means for substantially eliminating parasitic effects of said side radiators from said central radiator comprising a transmission line interconnecting said side radiators, said transmission line being substantially electrically equal to an odd integral multiple of a half wavelength at the operating frequency.

7. Radio beacon system affording quadrantal indications, including a first beacon unit arranged to produce a first set of two overlapping radiation patterns defining a course line, means for supplying continuous audible frequency modulation signals difiering for each of said patterns, a second beacon unit arranged to produce a second set of two other overlapping radiation patterns, said first and said second sets of radiation patterns respectively defining discrete course lines positioned at ninety degrees to one another, and means for producing differing keyed audible modulation signals for each of said patterns of said second set, whereby received signals from said system have two sets of characteristic modulation signals, each set including two difiering signals and whereby four permutations of received signals are possible, each permutation defining a predetermined quadrantal position. ANDREW ALFORD. 

